It is known to produce monoolefin oligomers by use of boron trifluoride as the catalyst together with a co-catalyst component. A variety of co-catalysts have been proposed for this use including water, alcohols, ethers, esters, aldehydes, ketones, and acid anhydrides. Oligomers produced in this manner are useful in the production of synthetic lubricating oils of different viscosities. Typically the production of such products, often referred to as PAOs, involves oligomer fractionation, hydrogenation and back blending to achieve desired properties. Usually the dimers and triers, especially those of 1-decene, are of greatest utility in the production of low viscosity PAOs for various end use applications.
U.S. Pat. No. 4,045,507 to Cupples, et al. describes a multi-stage process for oligomerizing 1-decene which includes use of a series of two or more tank type reactors. The patentees found that the trimer to tetramer ratio decreases with increasing 1-decene conversion in both stages of a two-stage operation, and that this ratio is higher in the second and succeeding reactors. Thus the process described in the patent operates at low conversion in the first stage and at higher conversions in succeeding stages of the process. The patent shows in Examples 5 and 6 of Table I that at 1-decene conversions of 83.4% and 90.5%, the amount of dimer in the product was only 5.2% and 3.8%, respectively. In addition, the combined total of dimer and trier in the products was 47.8% at 83.4% conversion and 38.9% at 90.5% conversion.
To satisfy commercial requirements, it would be highly desirable to provide a single stage process which can be operated at high olefin conversions (e.g., above 90%) and which can produce a reaction mixture containing a combined total of dimer and trimer above 70%, and in which at least 20% (preferably at least 30% and more preferably at least 40%) of the reaction mixture is dimer. This invention makes it possible to achieve all of these goals.